SUMMARY
Neuropeptides exert broad effects across the brain to influence behavior. However, the mechanism by which the brain uses neuropeptide signaling to exert top-down control over complex behavioral responses remains poorly understood. Prolonged social isolation induces a distinct internal state that results in sweeping changes to behavior, including increased aggression. Here, we find that isolation-induced aggression activates Tachykinin-2 expressing (Tac2+) neurons in the mouse medial prefrontal cortex (mPFC). Genetic characterization of Tac2+cells in the mPFC reveals them to be a population of unexplored GABAergic neurons. In-depth behavioral analyses combined within vivorecordings of neural activity demonstrate that mPFC Tac2+neurons are tuned to distinct phases of isolation-induced aggression: investigatory behaviors that escalate to attack (aggression escalation) and attack itself (aggression release). Loss-of-function perturbations targeting the release of either Neurokinin B (NkB), the stimulatory peptide encoded byTac2, or the inhibitory neurotransmitter, GABA, reveal that these signaling molecules exert dissociable control over aggression escalation and release. These findings identify distinct roles for opposing signaling molecules co-released from the same population of cells. This suggests a surprising neurochemical mechanism by which neuropeptidergic populations in the prefrontal cortex exert top-down influence over complex behavior via the co-release of signaling molecules with opposing actions but coordinated impacts on behavior.